Climate change: how Obama and McCain compare

Climate change may not be one of the key topics in the US presidential election. But it underwrites many issues that are - most noticeably oil prices, energy security and nuclear power.

So what are the positions of Democrat candidate Barack Obama and Republican candidate John McCain on climate change? Here we comb various sources such as the candidates' manifestoes, their answers reported in Nature Reports: Climate Change this week, and a debate between two of the candidates' senior advisers.

On reducing US greenhouse gas emissions

Obama aims to bring domestic greenhouse gas emissions down to 1990 levels by 2020 and to 80% below these levels by 2050. He supports a strong limit on greenhouse gas emissions - also known as a "carbon cap" - and believes businesses should trade the right to emit greenhouse gases in a cap-and-trade scheme similar to the European one.

Unlike the European scheme, Obama believes polluters should not be given a number of free permits which they can then trade. Instead, he believes permits should be auctioned off to the highest bidder. "The choice not to auction is, in effect, a choice to give the permits to the incumbent polluters," says Dan Esty, an environmental law professor at Yale University who spoke on Obama's behalf in a debate in September. "Auctions create the incentive for people that can provide solutions to come into the market and help others solve their problems, help others not have to pay."

Obama says a carbon tax would be redundant to an effectively designed cap and says he would not pursue a combination of the two policies.

McCainalso supports a cap-and-trade system. He aims to reduce greenhouse gas emissions to 1990 levels by 2020 and to 60% below 1990 levels by 2050. He is not in favour of a carbon tax, nor of auctioning off emissions permits from the start.

On agreeing to binding emission limits within an international treaty

Obama believes the US must rejoin the international climate change negotiations. He does not believe the US should wait for China and India to agree to binding emissions before it does so, but he believes that those nations must not be far behind in making their own commitments. Obama believes that the immediate challenge is to develop the consensus in Congress needed to cap domestic emissions, and that domestic action will strengthen the US's ability to engage the international community in the Copenhagen process set to succeed the Kyoto Protocol.

McCain believes the US should not sign on to an international climate treaty unless China and India agree to participate. He also believes this is a necessary step to successfully pass climate legislation through Congress. However, McCain has said that if the efforts to include China and India in an international treaty fail, the US still has an obligation to act.

On investments into alternative and renewable energy

Obama says he will invest $150 billion over 10 years in the development and deployment of renewable energy, including a long-term extension of the production tax credit for renewable energy and the doubling of federal research and development funds for clean energy.

McCain says he will encourage a market for alternative energy technologies through cap-and-trade. He proposes to offer a $5,000 tax credit to consumers that purchase zero-emission cars and a $300 million prize for the development of battery technology that will bring plug-in hybrids and fully electric automobiles into commercial use.

On managing the costs of rising energy bills and reducing greenhouse gas emissions

Obama says he will take steps to reduce the burden of rising energy prices on US families, including an emergency energy rebate, a plan to reduce price speculation in the oil market and a programme to protect one million low-income homes from the effects of the weather.

McCain promises to use a portion of the profits generated by auctioning off cap-and-trade permits to provide relief to low-income families. But he does not support bringing in such an auction immediately.

On exploiting domestic oil reserves

Obama has reservations about drilling for oil development off US coastlines. He will however consider a package that provides meaningful advances towards a clean-energy future, while allowing for limited outer-continental shelf drilling.

McCain supports aggressive offshore drilling and plans to expand the exploration and production of domestic oil and natural gas. McCain traditionally has not supported drilling in the Arctic National Wildlife Refuge in Alaska, but has recently hinted that his position could change. His running mate, Sarah Palin, strongly supports drilling in the Refuge.

On coal power stations and carbon capture and sequestration

Obama would also devote part of the revenue from the auction of emissions permits to the development and deployment of carbon capture and storage technology. He supports developing five commercial-scale, coal-fired power plants capable of capturing their carbon emissions and storing them away with the private sector.

Obama told Nature that it will be difficult to aggressively reduce greenhouse gas emissions without nuclear power and that all-non-carbon forms of energy (which include nuclear) must be investigated. Obama does not believe that the Department of Energy's proposed underground nuclear waste storage facility at Yucca Mountain is a suitable site for the permanent disposal of the entire nation's nuclear waste. "Let's not torque the choice toward nuclear," said Esty. "McCain favours a big commitment to nuclear power that could involve expenditures of $300 billion that may or may not be the right path forward."

McCain believes nuclear power should comprise a significant portion of US energy production. "We all know in the end, that addressing global warming is about innovation and new technologies," said Douglas Holtz-Eakin, former director of the Congressional Budget Office, who presented McCain's views at the debate at which Esty spoke for Obama. "But there is one zero-emissions technology that's out there right now, that we can take advantage and Senator McCain believes we should take advantage of it in an aggressive way." McCain wishes to construct 45 new nuclear power plants by 2030 and eventually to build 100 new plants. He believes that nuclear waste could be safely stored at Yucca Mountain.